Use a sum or difference identity to find the exact value of sin225°

a) is the sine of 285

b) is the sine of 15, 165
c) is the sine of 75, 105
d) is the sine of -15, 195

check my thinking.

it's B?

none of the given answers is correct.

Are you sure you typed it correctly?

sin 225 = sin(180+45)
= sin180cos45 + cos180sin45
= 0 + (-1)√2/2
= -√2/2

no those are the options for sure :/

Are you sure it is not

> Use a sum or difference identity to find the exact value of sin255

To find the exact value of sin225° using a sum or difference identity, we can use the identity:

sin(A ± B) = sinA * cosB ± cosA * sinB

In this case, we can express 225° as the sum of two angles: 180° and 45°. So, we have:

sin225° = sin(180° + 45°)

Using the sum identity, we can rewrite this as:

sin225° = sin 180° * cos 45° + cos 180° * sin 45°

Because sin 180° = 0 and cos 180° = -1, we can simplify this further:

sin225° = 0 * cos 45° + (-1) * sin 45°
= -sin 45°

Since sin 45° can be written as √2 / 2, we have:

sin225° = -√2 / 2

Therefore, the correct answer is not option A.